Alkali metal cations often show pronounced ion specific interactions and selectivity with macromolecules in biological processes, colloids, and interfacial sciences, but a fundamental understanding about the underlying microscopic mechanism is still very limited. Here we report a direct probe of interactions between alkali metal cations (M+) and dicarboxylate dianions, O2C(CH2)nCO2 (Dn2-) in the gas phase by combined photoelectron spectroscopy (PES) and ab initio electronic structure calculation on nine M+Dn2-complexes (M = Li, Na, K; n = 2, 4, 6). PES spectra show that the electron binding energy (EBE) decreases from Li+ to Na+ to K+ for complexes of M+–D2 2-, whereas the order is Li+
Revised: March 23, 2012 |
Published: February 10, 2012